Citation:
Abstract:
We present one of the most precise measurements to date of the spatialclustering of X-ray-selected active galactic nuclei (AGNs) using asample derived from the Chandra X-ray Observatory survey in theBoötes field. The real-space two-point correlation function over aredshift interval from z = 0.17 to z ~ 3 is well described by the powerlaw, ξ(r) = (r/r 0)-γ, for comovingseparations r <~ 20 h -1 Mpc. We find γ = 1.84± 0.12 and r 0 consistent with no redshift trendwithin the sample (varying between r 0 = 5.5 ± 0.6 h-1 Mpc for langzrang = 0.37 and r 0 = 6.9± 1.0 h -1 Mpc for langzrang = 1.28).Furthermore, we are able to measure the projections of the two-pointcorrelation function both on the sky plane and in the line of sight. Weuse these measurements to show that the Chandra/Boötes AGNs arepredominantly located at the centers of dark matter halos with circularvelocity v max > 320 km s-1 or M180 > 4.1 × 1012 h -1 Msun, and tend to avoid satellite galaxies in halos of this orhigher mass. The halo occupation properties inferred from the clusteringproperties of Chandra/Boötes AGNs—the mass scale of theparent dark matter halos, the lack of significant redshift evolution ofthe clustering length, and the low satellite fraction—are broadlyconsistent with the Hopkins et al. scenario of quasar activity triggeredby mergers of similarly sized galaxies.